In this section

Blue duck/whio conservation

Did you know?

Whio use the river as a defence mechanism to evade threats – they go with the flow, submerse themselves, then retreat into roosts.

A unique taonga

Blue duck/whio are a taonga (treasured) species that Māori have a strong cultural, spiritual, and historic connection with.

Their Māori name is whio in the North Island or ko whio whio in the South Island, which depicts the call of the male bird. They are forever watchful – they will always see you before you see them, and the male will sound the alarm call.

Whio are believed to be an ancient species of waterfowl, that appeared at a very early stage in evolutionary history. Their isolation in New Zealand has resulted in unique anatomical and behavioural features.

The whio is an iconic back-country species, and it features on the New Zealand $10 note.

The blue duck is a river specialist, and one of the few waterfowl worldwide that live year round on fast-flowing rivers.

They are a key indicator of healthy rivers and streams. They require clean, fast flowing streams in the forested upper catchments of rivers that provide high water quality, low sediment loadings, stable banks, over head canopy cover, and lots of varied invertebrate communities. The more breeding pairs of blue duck the healthier the river.

Fight for survival

Blue duck are found no where else in the world, and are rarer than some species of kiwi.

They were once widespread throughout New Zealand. Today they are limited to the less modified catchments of the Urewera, East Cape and central areas of North Island; and along the West Coast of South Island from Nelson to Fiordland.

Populations are now patchy and isolated. They have low reproductive success, and there are more males than females. There are around 640 pairs on the North Island, and just under 700 pairs on the South Island – a total population between 2,000 and 3,000, and that's declining.

Unless the causes decline are remedied (or reduced), the species faces a very real risk of becoming extinct.

Whio have adapted to a harsh environment that is prone to flooding. They nest along the riverbank in shallow, twig, grass and down-lined scrapes in caves; under river-side vegetation; or in log-jams, dry punga fronds, and toi toi. Floods can destroy nests, change the shape of the river, separate families, wash away food sources, and force whio into side streams where they lose the water as their first defence. All this can have an extreme impact on breeding success, and a significant impact on whio populations.

Their habitat has been reduced by the clearance of vegetation from stream and river banks, water diversions, poor water quality, and damming for hydro-electric and irrigation schemes

Even where high quality river habitat remains, predation by introduced mammals is causing a significant decline of the species.

Stoats are the greatest danger. Whio nest in the same areas where stoats commonly feed. Stoats can easily follow the scent trail of the female to her hiding place, or sniff out the nest through scent carried on the breeze blowing up and down the river. They attack females on the nest, steal eggs, and take young ducklings from the river’s edge.

Feral cats, domestic dogs, and ferrets are also known predators. Rats and possums have been recorded at nests and are likely to take eggs.

During the late summer moult period, blue duck are flightless making them even more vulnerable to attacks.

Unlike some endangered bird species, blue ducks cannot simply be transferred to off-shore islands, because they rely on large areas of quality, fast flowing riverine habitat that is unavailable on islands. The continued survival of this species is therefore largely dependent on the protection of secure source populations throughout mainland New Zealand.

Threat management

Whio are scattered along the river in 1–5 km territories. They need a scale of management like no other species to ensure their survival. This can be extremely challenging and requires significant resources to manage their threats.

In Te Urewera we found 90% of nests failed in an area without predator control. Of the females, 46% were killed during the moult period when they retreated up small side stream to avoid disturbance.

In the Ruahines and in Taranaki, over 60% of the fledged juveniles died in areas outside of management. From a sample of 154 whio deaths recorded between 1989-2008, 89 were linked to predators (58%), 24 natural deaths, 22 human causes, and 19 were unknown. Stoats were the cause of 79 of the 89 predator deaths.

Battle for our Birds is DOC's successful national pest control programme that protects whio and other native species from predators.